Port: win32 DLLs don't support hidden symbols

Signed-off-by: Michael Jeanson <[email protected]>
Signed-off-by: Jérémie Galarneau <[email protected]>

src/common/macros.h

@@ -74,7 +74,14 @@ void *zmalloc(size_t len)
 #define LTTNG_PACKED __attribute__((__packed__))
 #endif
 
-#ifndef LTTNG_HIDDEN
+/*
+ * LTTNG_HIDDEN: set the hidden attribute for internal functions
+ * On Windows, symbols are local unless explicitly exported,
+ * see https://gcc.gnu.org/wiki/Visibility
+ */
+#if defined(_WIN32) || defined(__CYGWIN__)
+#define LTTNG_HIDDEN
+#else
 #define LTTNG_HIDDEN __attribute__((visibility("hidden")))
 #endif